Why buy a headlamp? It's simple: wherever you look, the light follows. This leaves your hands free to strip down a water filter, change a bike tire, or read a book while lying in your sleeping bag. And as with many technologies, headlamps have become lighter and more affordable.
The description on the headlamp's packaging or on a website should include an estimate of how far the light beam can reach and still be effective. Imagine that you are cross country skiing, mountain biking, on in some other way moving quickly in the dark. In those cases, the headlamp should have a maximum range of at least 50 meters. If you are just putzing around camp, a range of 20 meters is fine.
Like to read with your headlamp? Get one with a body that can tilt downwards towards the book.
If you run with a headlamp, keep the weight to a minimum. Five ounces or less should work (including batteries). For more sedentary pursuits the weight is less of a concern. Most all of the headlamps sold by Eastern Mountain Sports are relatively lightweight.
Headlamp Brightness Settings
Headlamps often provide more than one brightness mode. This gives the user the option of keeping the light dim to save batteries, bright when you're moving at night, or maybe somewhere in between. If you will be using the headlamp for a variety of activities, choose one with at least 3 brightness modes
Headlamp Strobe Modes
A strobe mode with the headlamp blinking rapidly will make you more visible to vehicles. Also, it's less of a drain on the batteries.
Headlamp Battery Life
Consider the max battery life when choosing a headlamp. After all, batteries aren't cheap. The average battery life for headlamps kept at low setting is about 130 hours (much better than most flashlights).
If you rock climb at night, or if there's a chance that you might be stuck on the crag at sundown, consider buying a headlamp that has a built-in low-battery indicator. You don't want to be surprised in a situation like that.
Off Trail Adventuring
Buy a headlamp with no external wires if you frequently bushwack through heavy undergrowth. That way branches will have less to snag on.
When dayhiking, always keep a light source in your pocket or pack, even if you plan to be back to the house or car way before nightfall.